1. Field of the Invention
The present invention pertains to tire finishing equipment and the related arts. More specifically, the present invention provides an expandable tire hub suitable for use with present day tire finishing equipment including means for rotating the hub and performing operations in conjunction therewith.
2. General Background
The use of vehicles employing pneumatic tires has resulted in the development of the retreading industry as the carcass of a tire represents the significant cost thereof and it is often more economical to retread the tire than replace it in its entirety. For retreading tires, the retreading industry has developed many sophisticated and complex pieces of equipment and machinery to not only maximize production, but additionally to provide a more durable and safe product. Conversely, these engineering efforts have resulted in even greater use of retreads for all types and sizes of vehicles.
Perhaps the first major step in preparing a tire carcass to be retreaded is the buffing operation which requires that the outside peripheral surface of the tire be ground or buffed down. This is accomplished on a tire buffing machine comprising an inflated hub member upon which the tire is rotatably mounted. Upon rotation of the tire, the outside peripheral or treaded surface, that is, the surface which contacts the ground, is accordingly buffed down. Such tire finishing equipment would generally comprise a grinding wheel operably mounted upon the tire rotating machine and related appurtenances.
One of the major problems the retreading industry faces in the preprocessing of a tire carcass is to produce a product which is balanced as close as possible or is not very much out of round. Thus, the hub upon which a tire carcass is placed for buffing must be very accurate such that once a tire is placed thereon and it is expanded, and then the tire subsequently inflated, the tire will be concentrically mounted relative to the axis of rotation. Otherwise, the outer peripheral surface of the tire will be buffed such that it will not be concentric with the tire rim. Under such conditions, the subsequent retreading of the tire will produce a product which is out of balance. It is a well established fact in the retread arts that one of the major problems with retreads is due to the fact that they are difficult to balance caused by the above problem.
The more popular type of inflated hub employed in the art today comprises a semi-mechanical type of hub incorporating a central cone type member which is in sliding frictional contact with a series of vanes extending outward simulating a spoked tire. The individual vanes or spokes of the wheel in turn are connected to rim or hub portions and the centrally located cone member is generally actuated along its longitudinal axis so as to cause the vane members to move in and out radially. An expandable round rubber casing member is fixed over the segmented rim members. In operation, the hub is deflected whereby the cone member is withdrawn, a tire placed thereon, the cone member is shoved inwards so as to expand the segmented rim members out into contact with the beads or inside rim of the tire is then inflated by virtue of a source of pressurized air injected through the casing member. Typical of this type of hub is that as disclosed in U.S. Pat. Nos. 2,936,676 and 2,960,130.
Present-day expandable hubs still leave much to be desired in their performance, especially in light of the fact that the industry has been subjected to close scrutiny by the federal government to meet greater specifications for retreads. Typical disadvantages of these present-day expandable hubs are that due to their mechanical features whereby metal is in contact with metal at the greater points of stress, considerable wear is experienced. Conversely, these mechanical or semi-mechanical hubs require constant oiling which presents a problem due to the amount of grit and by-product rubber produced in the work zone. Additionally, by virtue of the mechanics of these prior art devices, they have limited expansion such that a single hub will only accommodate a narrow range of different sizes of tires. Needless to say, the different sizes of tires are virtually unlimited. Additionally, the frictional and wear problems encountered in these prior art hubs make it difficult to maintain a high degree of roundness accuracy as the wear increases due to the particular mechanical design. The problem is yet complicated by the fact that the type of wear is not a compensating wear such that the roundness would be maintained within a certain specification, but rater, continues to increase directly proportional to the wear.
The present invention clearly overcomes the above prior art problems and has for its objectives the provision of an expandable hub exhibiting such advantages and features as being air over hydraulics such that it does not experience a non-compensating wear problem by virtue of the fact that it has no metal to metal contact at its points of stress. Moreover, by virtue of the present device being hydraulic, it remains constantly oiled. Another very distinguishing feature is that for a given hub size, it has a much greater expansion factor whereby it can accommodate a much greater range of different tire sizes. The net result is a substantial savings to the retreader both in the initial cost of the hub as well as in increased production due to the fact that a worker need not change the hub as much during retreading operations. Of even more significance is the fact that it maintains its roundness accuracy throughout its life, which includes the capability of the present hub to compensate for wear. The above, together with other features and advantages of the instant invention, will become apparent to one skilled in the art in light of the details of construction and operation of the present expandable tire hub device as shown in the drawings and described in the ensuing detailed disclosure of its preferred embodiments as particularly pointed out in the appended claims.
Therefore, it is an object of the present invention to provide an improved expandable tire hub apparatus for accommodating a wide range of tire sizes;
It is a further object of the present invention to provide an expandable tire hub apparatus utilizing the concept, air over hydraulics;
It is a further object of the present invention to provide an expandable tire hub apparatus which assures the peripheral tire surface to be concentric with the tire rim;
It is still a further object of the present invention to provide an expandable tire hub for concentrically mounting a tire thereupon and simultaneously inflating the tire for workover.